The reality of global climate change is motivating efforts to reduce the emission of human-produced CO2 and other greenhouse gases into the atmosphere. The combustion of fossil fuels such as coal, gasoline, and diesel is a major source of CO2 emissions and contributes to increasing levels of CO2 in the atmosphere. Carbon neutral alternatives to fossil fuels, including biodiesel and ethanol are limited by their limited supply, costs of production, and their requirement for farmland that may be needed for food production. There remains a need for carbon neutral alternatives to diesel, gasoline, and other fuels produced from oil.
Processes for the production of synthesis gas (syngas) are known in the art. For example, WO 2011/008263 A2 discloses the use of plasma gasification or pyrolysis for production of synthesis gas followed by the production of hydrogen from the synthesis gas in a water gas shift reaction and the production of products in various types of reactors.
WO 2011/002527 A1 discloses a method in which syngas is generated from a waste and water using a plasma melter, hydrogen is extracted from the syngas using a water gas shift reaction, and a C9 fuel is synthesized from the extracted hydrogen and syngas in a Fischer-Tropsch type reactor. The carbon for fuel synthesis is provided by the exhaust from a plant exhaust (e.g. a power plant exhaust), which is passed through a plasma chamber and then to a Fischer Tropsch reactor.
WO 2009/091325 A1 discloses a biomass gasification method and apparatus for production of syngas with a rich hydrogen content; and U.S. Pat. No. 5,584,255 discloses a method and apparatus for gasifying organic materials. U.S. Pat. No. 6,958,136 discloses a process for the treatment of nitrogen-containing waste streams that can generate syngas from carbon sources using alkalai metals and carbon radical formation.
Processes for synthesizing methane from syngas are known. For example, the methanation reaction converts syngas into methane and water in the presence of a catalyst (e.g. Ni/NiO, Ru, Cu, Pt, Rh) at temperatures between 150° C. and 600° C. PCT/NO2007/000387 discloses a process for making methane from CO, CO2 and H2 involving the production of H2 and O2 by splitting water. Jianjun Guo et al. (2004) Applied Catalysis A: General 273(1-2): 75-82 discloses the production of methane over nickel catalyst on magnesium aluminate spines. M. Wisniewski et al. (2005) Catalysis Communications 6(9): 596-600 discloses Catalytic CO2 reformation of methane over Ir/Ce0.9Gd0.1O2-x. U.S. Pat. No. 7,087,651 discloses a process and apparatus for steam-methane reforming.
Syngas may also be converted into a wide range of useful liquid hydrocarbons fuels and/or alcohols using the Fisher-Tropsch (F-T) process. US 2007/0129449 discloses a method and installation for producing liquid energy carriers such as methanol from a solid carbon carrier. The method involves the production of O2 and H2 by water electrolysis and gasifying a carbon carrier such as biomass or brown coal in a fluidized-bed gasifier in the presence of the produced O2. The raw synthesis gas is transferred to a heat exchanger where the temperature is reduced and the cooled syngas is mixed with the produced H2 to form methanol. The production of hydrocarbon fuels such as diesel and gasoline are not described, however, and the installation as described is not suitable for F-T reactions forming diesel or gasoline. The process is dependent on the production of O2 and H2 by electrolysis, which requires significant amounts of electrical power. The use of a fluidized thermal catalytic gasifier for the production of synthesis gas involves thermal catalytic methods such as counter-current fixed bed (“up draft”) gasification, co-current fixed bed (“down draft”) gasification, and entrained flow gasification, which produce significant amounts of tar that must be disposed of or used.
WO 2008130260 A1 discloses a waste to liquid hydrocarbon refinery system designed to convert municipal and industrial wastes, biomass, and other carbon-containing feedstocks into diesel, gasoline, and other products. The system involves a high temperature liquid iron bed that generates raw syngas from solid and liquid feedstocks and a very high temperature plasmatron to convert contaminants in the raw syngas into ions. A hydrocarbon synthesis subsystem converts the purified syngas into desired products. The system is designed to minimize the release of toxic waste into the environment but is relatively complex and expensive, requires relatively large amount of energy, and releases considerable amounts of carbon into the atmosphere.
EP 0221679 A2 discloses a process for producing liquid hydrocarbons from biomass involving the production of synthesis gas from biomass and synthesizing liquid fuels from the produced synthesis gas. Syngas is produced using a fluidized bed gasification system containing olefins. Liquid fuel containing C7 to C17 paraffinic hydrocarbons is produced from the synthesis gas, along with propanol and water, using a catalytic liquefaction. The process is designed to be economically viable but does not deal with pollutants such as NOx and SOx produced from biomass or the production of fuels from carbon-containing sources comprising municipal or industrial wastes. The process is not designed to be carbon neutral.
There remains, therefore, a need for carbon-neutral processes, apparatus, and systems for producing liquid hydrocarbon fuels from carbon-containing materials including biomass, wastes from municipal, medical and industrial sources, and coal. Additionally, there remains a need for processes, apparatus, and systems that remove NOx and/or SOx produced by the combustion of renewable and fossil fuels containing nitrogen and/or sulfur. The present invention in one or more aspects fills the aforementioned needs in the art by providing low emission and energy conserving systems and processes for producing useful fuels from a wide variety of carbon-containing source materials.